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Abstract:

A method for the manufacture of container preforms in which recycled
plastic material is subjected to at least one heat treatment in a
recycling machine before it is transferred to a preform machine, where at
least a major portion of heat introduced into the plastic material during
its heat treatment and storage is transferred from the recycling machine
with the plastic material into the preform machine. In a plant embodied
for carrying out the method, the recycling machine is coupled with the
preform machine either directly or via at least one intermediate storage
such that at least a major portion of heat introduced in the recycling
machine during a heat treatment of the plastic material can be
transferred with the plastic material into the preform machine.

Claims:

1. Method for the manufacture of container preforms from recycled plastic
material, in particular from PET flakes, comprising subjecting the
plastic material to at least one heat treatment in a recycling machine
before the plastic material is transferred to a preform machine, and
transferring at least a major portion of the heat that is introduced into
the plastic material during its heat treatment and storage from the
recycling machine with the plastic material into the preform machine.

2. Method according to claim 1, transferring the recycled plastic
material is transferred predominantly in the form of flakes from the
recycling machine either directly or via an intermediate storage in
absence of atmospheric oxygen at a temperature that is above the glass
transition temperature of about 65.degree. C. to 70.degree. C.

3. Method according to claim 2, transferring the recycled plastic
material from the recycling machine to the preform machine at a
temperature of about 180.degree. C.

4. Plant for the manufacture of container preforms from recycled plastic
material, in particular PET flakes, comprising at least one preform
machine forming preforms, which machine can be fed with the recycled
plastic material from at least one recycling machine providing the
recycled plastic material, the recycling machine is connected to the
preform machine either directly or via at least one intermediate storage
such that at least a major portion of heat introduced into the recycling
machine during a heat treatment of the plastic material can be
transferred with the plastic material into the preform machine.

5. Plant according to claim 4, wherein the preform machine comprises at
least one extruder that can be supplied with the plastic material and
injection molds, and that the recycling, machine comprises at least one
reactor in which heat treatment can be carried out.

6. Plant according to claim 5, wherein the recycling machine comprises at
least one decontamination reactor.

7. Plant according to claim 5, wherein the recycling machine comprises at
least one SSP reactor.

8. Plant according to claim 5, wherein the recycling machine comprises at
least one decontamination reactor and at least one SSP reactor.

9. Plant according to claim 5, wherein the decontamination reactor and/or
the SSP reactor of the recycling machine and the extruder of the preform
machine are combined in a block directly or via the at least one
intermediate storage, and that the block is advantageously embodied to be
heat-insulated and/or at least essentially free from oxygen.

10. Plant according to claim 9, and wherein a heat supply is connected to
the block.

11. Plant according to claim 9, and wherein a return means for discharged
defective preforms is provided between the preform machine and the
recycling machine.

12. Plant according to claim 4, wherein the preform machine is directly
combined in a block with a blow-molding machine.

13. Plant according to claim 12, and wherein a return means for waste
material and/or discharged defective containers of the blow-molding
machine is provided between the blow-molding machine and the recycling
machine.

14. Plant according to claim 4, wherein the at least one perform machine
is an injection molding machine.

15. Plant according to claim 7, wherein the at least one SSP reactor
comprises at least one combined decontamination and SSP reactor.

16. Plant according to claim 8, wherein the at least one decontamination
reactor and at east one SSP reactor are arranged downstream.

17. Plant according to claim 9, wherein the at least one intermediate
storage is a silo.

Description:

CROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application claims the benefit of priority of German
Application No. 102010002054.0, filed Feb. 17, 2010. The entire text or
the priority application is incorporated herein by reference in its
entirety.

FIELD OF THE DISCLOSURE

[0002] The disclosure relates to a method as well as to a plant for
manufacturing container performs, such as in beverage bottling
operations.

BACKGROUND

[0003] The manufacture of container preforms from recycled plastic
material, in particular PET flakes, requires a very heat-intensive
process. Moreover, the provision of recycled plastic material, in
particular PET flakes, requires enormous heat supply to decontaminate the
plastic material and optionally carry out an SSP treatment for
processing. The SSP treatment is a standard process known in the field of
PET plastic technology and means that an influence on the molecular chain
(extension, shortening or maintenance) is performed (solid state
polycondensation), i.e. a heat treatment over a certain period.
Decontamination and SSP treatment can be carried out in a recycling
machine in one reactor or in separate reactors, as is disclosed in DE 10
2005 013 701 A1. Decontamination is performed e.g. with hot gas, for
example air or nitrogen, where heat is supplied via different heat
transfer media until temperatures of, for example, between 100° C.
and 180° C. are reached. The SSP treatment is carried out e.g.
under subatmospheric pressure conditions, where temperatures up to at
most the melting temperature of the plastic material of 150° C. to
250° C., preferably between 170° C. and 210° C. are
set. The SSP treatment can run in an inert gas atmosphere, e.g. using
nitrogen or carbon dioxide. In the recycling machine known from DE 10
2005 013 701 A1, after the SSP treatment, the recycled plastic material
is cooled in a cooling reactor to a temperature between 50° C. and
100° C., preferably even to below 70° C., i.e. to a
temperature below the second order transition temperature of the plastic
material. For cooling, a cooling coil, a vibratory hopper conveyor, or a
fluidized reactor, or another cooling device can be used, for example by
supplying ambient air. Although at least the SSP treatment can be carried
out in batches, by a multi-part SSP reactor arrangement, a quasi
continuous discharge of recycled plastic material can be achieved. The
recycled plastic material cooled to below 65° C. is then fed to a
preform machine, or it is optionally previously completely cooled to room
temperature. In the preform machine, the recycled plastic material then
must be reheated to be able to produce the preforms.

BRIEF SUMMARY OF THE DISCLOSURE

[0004] One aspect of the disclosure is to provide a method and a plant for
the manufacture of container preforms from recycled plastic material
which permit at least an improved thermal balance in view of a
considerable saving of primary thermal energy.

[0005] As at least a major portion of the introduced and stored heat
required by the process for the provision of the recycled plastic
material is transferred into the preform machine, the heat demand in the
preform machine is significantly reduced, so that the thermal energy
balance can be considerably improved in the manufacture of container
preforms from recycled plastic material, supported, as an accompanying
effect, by the elimination of the expenditure of time and the energy
demand for cooling the recycled plastic material before it is transferred
to the preform machine.

[0006] The connection of the recycling machine with the preform machine
ensures in the plant that the recycled plastic material does no longer
have to be force-cooled but is transferred into the preform machine such
that at least a major portion of the heat introduced into the recycling
machine during the heat treatment of the plastic material is transferred
to the preform machine. Thus, the heat requirement of the preform machine
is reduced and an advantage is achieved for the device in that a cooling
unit for forced cooling of the recycled plastic material can be omitted.

[0007] In a functional method variant, the recycled plastic material,
which is preferably provided predominantly in the form of flakes e.g. of
PET, is transferred into the preform machine either directly or via an
intermediate storage and in absence of atmospheric oxygen at a
temperature that is in any case above the glass transition temperature of
about 65° C. to 70° C. In this manner, heat is saved in the
preform machine which would be required initially to bring recycled cold
plastic material to this temperature again. Moreover, the duration of the
process is shortened as forced cooling is eliminated. The at least
substantial absence of oxygen in the transfer of the recycled plastic
material into the preform machine excludes influences on the recycled
plastic material that affect processing quality.

[0008] In a particularly functional way, the recycled plastic material is
transferred into the preform machine at a temperature of at least about
180° C., so that for reaching the processing temperature of the
recycled plastic material in the preform machine, now only low heat
supply is required.

[0009] In a functional plant variant, the preform machine comprises at
least one extruder supplied with the recycled plastic material and
injection molds in which the preforms are manufactured. The recycling
machine, which is combined in a block with the preform machine directly
or via the intermediate storage, comprises at least one reactor,
preferably at least one decontamination reactor, and a downstream SSP
reactor, or at least one reactor in which decontamination and a further
treatment, e.g. an SSP treatment, are carried out together. To achieve a
quasi continuous discharge of recycled plastic material, it can be even
functional to provide multi-part decontamination and SSP reactors, or
several reactors operated in an alternating and/or overlapping manner, or
operated in combination. Furthermore, several preform machines can be fed
with still hot recycled plastic material from the recycling machine
simultaneously or in an alternating manner.

[0010] In a functional plant variant, a reactor, e.g. the decontamination
reactor or the SSP reactor, and the extruder are combined in a block
directly or via the at least one intermediate storage, preferably a silo.
The combination in a block can preferably be heat-insulated and/or
embodied such that the transfer of the recycled plastic material is
effected at least substantially without the presence of oxygen. The
absence of oxygen permits to carry out the transfer with a maximum
portion of the heat introduced into the recycling machine without
compromising the processing quality of the hot plastic material by the
transfer.

[0011] In a functional plant variant, the combined block can even be
connected to a heat supply which contributes to the increase or
maintenance of the temperature of the plastic material during transfer
and is possibly also fed by heat supply means of the recycling machine
and/or the preform machine.

[0012] It is furthermore advantageous to provide a return means for
discharged defective preforms between the preform machine and the
recycling machine. In this manner, the defective preform discharge can be
directly returned into the recycling machine without having to be
intermediately stored, cooled and later reheated.

[0013] Furthermore, in view of an advantageous thermal energy balance, it
can be advantageous to combine the preform machine directly in a block,
preferably via a preform heat treatment section for adjusting a certain
temperature profile in each preform, with a blow-molding machine. In this
manner, heat from the preform machine can also be transferred into the
heat treatment section or directly into the blow-molding machine.

[0014] Here, a return means for waste material and/or discharged defective
containers can be suitably provided between the blow-molding machine and
the recycling machine, so that the waste material or the discharged
defective containers do not have to be separately stored, cooled and
either rejected or recycled in another way. The return means altogether
prevent a waste of plastic material.

BRIEF DESCRIPTION OF THE DRAWING

[0015] Embodiments of the subject matter of the disclosure are illustrated
with reference to the drawing.

[0016] The FIGURE is a schematic representation of a plant for the
manufacture of container preforms in accordance with the disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0017] The plant A in the FIGURE is for the manufacture of container
performs P, as an option with a direct block combination with a
blow-molding machine B for the manufacture of blow-molded or stretch-blow
molded hollow plastic containers, in particular PET bottles F, in
particular PET flakes, and this in e.g. a continuous procedure.

[0018] More specifically, plant A for the manufacture of container
preforms P in the FIGURE essentially consists of a recycling machine R
for recycled plastic material K which is directly connected to a preform
machine M, e.g. for injection-molding the preforms P, via a block 12. The
block 12 can preferably be at least one intermediate storage 20 for hot
recycled plastic material K, such as a silo or the like.

[0019] The essential components of the recycling machine R are at least
one reactor, e.g. a decontamination reactor 1 and an SSP reactor 2
downstream thereof, or are combinable with it. The reactor, e.g. the
decontamination reactor 1, is fed with plastic material via a metering
device 3 (or as an alternative from a device for producing flakes), the
plastic material predominantly consisting of flakes, preferably PET
flakes from PET bottles.

[0020] The plastic material is subjected to a heat treatment in the
reactor, e.g. in the decontamination reactor 1, e.g. within a temperature
range T1 between 20° C. to 200° C., preferably within a
temperature range around about 150° C., and over a treatment
period that depends, among other things, on the particle size of the
flakes. In the process, heat of at least one heat source 4 can be
supplied to the reactor.

[0021] In the SSP reactor 2, a molecular chain length influence of the
plastic in its solid state (solid state polycondensation) is effected, if
provided, where further decontamination can also take place (combination
reactor). This is done e.g. over a predetermined process duration within
a temperature range T2 of about 150° C. to 250° C.,
preferably between about 170° C. and 210° C. Here, heat can
be supplied to the SSP reactor 2 from a heat source 5. The SSP process
preferably runs in an inert gas atmosphere (nitrogen or carbon dioxide)
in absence of atmospheric oxygen, optionally at subatmospheric pressure.

[0022] The recycled plastic material K is, indicated by an arrow 6,
transferred into the preform machine M at a temperature T3 which is above
a temperature of about 65° C. (glass transition temperature of the
plastic material), and is preferably about 180° C., this
temperature coming from a major portion of the heat supplied in the heat
treatment in the recycling machine R. If an SSP reactor 2 is provided,
the recycled plastic material K is directly transferred from the SSP
reactor 2 into the preform machine M by a block 12 which is embodied such
that the transfer and the heat transfer at least essentially take place
in absence of atmospheric oxygen. The block 12 can be embodied as
intermediate storage 20, e.g. as silo, and can comprise a heat insulation
13 and optionally even a heat source 14 for supplying heat, at least to
maintain the temperature T3, or even to increase it. At their hearts, the
recycling machine R and the preform machine are connected to each other
or combined in a block at least functionally, preferably even
structurally.

[0023] The preform machine M comprises e.g. at least one extruder 7 which
plasticizes the plastic material K and introduces it into injection molds
8 where the container preforms P continuously discharged at a discharge 9
are manufactured. Optionally, at least one further heat source 19 is
functionally assigned to the preform machine M.

[0024] The manufactured container preforms P can be subsequently stored
and cooled and forwarded to a blow-molding machine. In the embodiment in
FIG. 1, however, the plant A for manufacturing the container preforms P
from recycled plastic material K is directly combined in a block at least
with a blow-molding machine B to be able to utilize the heat of the
manufactured container preforms P to a maximum possible extent during
blow molding stretch-blow molding). The blow-molding machine B has, for
example, a blow rotor with non-depicted blow molds in which the
containers, for example the PET bottles F, are continuously produced. As
for blow-molding a certain temperature profile is required in each
container preform P, a heat treatment section 11 can be provided between
the preform machine M and the blow-molding machine B.

[0025] As two further options, which are provided either separately or in
combination, at least one return means 16 is provided between the
discharge 9 of the preform machine M and/or the blow-molding machine B to
return discharged defective preforms (sorting out device 15) from the
preform machine M and/or waste material and discharged defective
containers (sorting out means 17) from the blow-molding machine B each to
the recycling machine R, and this either to the metering or flake
production means 3, or via a separate crushing means 18 directly into the
decontamination reactor 1 (or the SSP reactor 2).

[0026] The recycling machine R can supply several preform machines M
simultaneously. To permit a quasi continuous procedure, at least two
recycling machines R, R' (or reactors 1, 2) can be assigned to one
preform machine M or several preform machines M, M'. The blow-molding
machine does not necessarily have to be combined in a block with the
preform machine M. The recycling machine R could also comprise only one
reactor which is used for decontamination and for the SSP process.

[0027] In the recycling machine R, preferably adiabatic process conditions
prevail. The heat sources 4, 5, 14, 19 can be operated with any arbitrary
heat transfer media (water, vapor, electrically, thermal oil, or the
like). As a further option, instead of the fixed block 12 between the
recycling machine R and the preform machine M, an interchangeable
container system could also be used, for example such that one
interchangeable container each is being filled with a hatch at the
recycling machine R, then closed and transferred to the preform machine M
and connected there, so that with at least two interchangeable
containers, a quasi continuous operation is permitted. These
interchangeable containers can be heat-insulated or even heated.